Display screen or portion thereof with transitional graphical user interface



FIG. 1 is the first image in a sequence for a display screen or portionthereof with transitional graphical user interface showing our newdesign; and,

FIG. 2 is the second image thereof.

The outer perimeter shown in broken lines in the drawings illustrates adisplay screen or portion thereof and forms no part of the claimeddesign. The remaining broken lines in the drawings illustrate portionsof the graphical user interface that form no part of the claimed design.

The appearance of the transitional image sequentially transitionsbetween the images shown in FIGS. 1-2. The process or period in whichone image transitions to another image forms no part of the claimeddesign.

CLAIM The ornamental design for a display screen or portion thereof withtransitional graphical user interface, as shown and described.